1. Field of the Invention
The present invention relates to a brush-holder fitting, especially for a motor-vehicle starter.
2. Description of the Related Art
A brush-holder fitting is already known, especially from FR 2.389.253, including two components fixed to one another by means of elastic locking tabs. One of these two components is a seating intended to be affixed onto a bearing, while the other is a guide component which defines two cages in which the brushes are trapped with their springs when the said guide component is in place on the seating.
In order to make it possible to provide for these two components to be centred on the bearing, the seating features several orifices intended to accommodate centring pins carried by this bearing. Moreover, it is traversed by a cylindrical hub within which is accommodated an annular element called xe2x80x9cbushxe2x80x9d which is intended to provide rotational guidance of the shaft of the machine.
As will be understood, such a construction poses a problem of leaktightness and makes it necessary to provide, between the seating and the bearing, special purpose means for preventing any water penetration within the latter.
A bearing made of plastic is also known, especially from FR 2.536.602, which carries guide cages which are of a piece with the said bearing and which are moulded with it.
However, with such a bearing, putting the brushes and their springs in place in the guide cages proves to be a delicate task, since it is necessary, at the same time, to mount the bearing onto the chassis, mount the brushes and the springs within their cages, and centre the assembly with respect to the chassis of the electric machine and to the shaft of the rotor.
Moreover, this solution is not mechanically satisfactory, since the moulded bearing has a tendency to be deformed under the force of the tie rods which fix it to the chassis. The creep due to the ambient temperature aggravates this phenomenon.
One object of the invention is to remedy the drawbacks of the brush-holder fittings known at the present time and to propose a leaktight fitting, which is very simple to produce and has a reduced number of components.
To that end the invention proposes a brush-holder fitting for an electric machine including two components affixed to one another, one which features several guide cages which each accommodate one brush and at least one elastic element, the other which constitutes a component forming a seating which includes means allowing it to be assembled onto a metal bearing, the component forming a seating including a hub accommodating an annular element intended to provide rotational guidance for the shaft of the machine, characterised in that the hub is closed at its extremity intended to be opposite the shaft of the machine, the seating-forming component being able, by itself, to ensure leaktightness with respect to the bearing.
Advantageously, the seating-forming component features fixing pins intended to pass through complementary holes of the bearing.
This component forming the support plate also features fixing pins intended to pass through complementary holes of the brush-guidance component.
By flattening the pins, for example during an operation of hot riveting or by ultrasonic welding, it is possible to obtain leaktight fixings while making it possible to take up the manufacturing tolerances.
Clearly, other systems of assembly can be used such as screws, rivets, etc., but that is less advantageous since its relies on supplementary components. The pins here are moulded integrally with the support plate.
This support plate is equipped with elastically deformable tabs suitable for interacting, by clipping, with the studs moulded integrally with the guide component.
It is thus possible to carry out temporary assembling of the support plate with the guide component then to affix this subassembly onto the bearing and carry out final assembly of the support plate, with the guide component and with the bearing taking up the forces for fixing the assembly thus constituted, onto the chassis of the electric machine, such as a starter.